Valve/sensor assemblies

ABSTRACT

In a first aspect, a valve/sensor assembly is provided that includes a door assembly. The door assembly has (1) a first position adapted to seal an opening of a chamber; (2) a second position adapted to allow at least a blade of a substrate handler to extend through the opening of the chamber; and (3) a mounting mechanism adapted to couple the door assembly to the chamber. The valve/sensor assembly also includes a sensor system having a transmitter and a receiver adapted to detect a presence of a substrate and to communicate through at least a portion of the door assembly. Systems, methods and computer program products are provided in accordance with this and other aspects.

The present application is a division of U.S. patent application Ser.No. 09/895,437 filed Jun. 30, 2001, now U.S. Pat. No. 6,553,280 whichclaims priority from U.S. Provisional Patent Application Serial No.60/216,981, filed Jul. 7, 2000. Both of these patent applications areincorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates to detection technology, and morespecifically to detection technology that is used to detect asemiconductor wafer.

BACKGROUND OF THE INVENTION

Semiconductor wafers are processed within automated fabrication toolscomprising a plurality of chambers. FIG. 1A is a schematic top planview, in pertinent part, of an automated semiconductor devicefabrication tool 11. The exemplary fabrication tool 11 of FIG. 1Acomprises a first transfer chamber 13 and a second transfer chamber 15.A first and a second wafer handler 17, 19, each having a blade (notshown) that may support a wafer, are housed in the first transferchamber 13 and the second transfer chamber 15, respectively. The firsttransfer chamber 13 and the second transfer chamber 15 are bothmonolithic and have various chambers coupled thereto.

A pair of loadlocks 21, 23 and a pair of pass-through chambers 25, 27are coupled to the first transfer chamber 13. Other chambers such asdegassing or oxide-etch chambers (shown in phantom) also may be coupledto the first transfer chamber 13. The pass-through chambers 25, 27 and aplurality of processing chambers 29, 31, 33, and 35, which areconfigured to perform various semiconductor device fabrication processes(e.g., chemical vapor deposition, sputter deposition, etc.), are coupledto the second transfer chamber 15. A controller 36 controls wafertransfer and processing within the fabrication tool 11.

Typically the environment of each chamber must be selectively isolatedfrom the environments of neighboring chambers to prevent crosscontamination, and to enable the various chambers to be maintained atpressures that differ according to the process to be performed therein.To achieve such selective isolation, each chamber is provided with aslit (not shown) through which one of the wafer handlers 17, 19 mayextend to transport wafers to and from the chamber. The slit of eachchamber is selectively sealed with a door assembly 37 (typicallyreferred to as a slit valve for vacuum applications, and as a gate valvefor non-vacuum applications).

As the wafer handlers 17, 19 transport a wafer through slits and throughvarious chambers, the wafer must be accurately positioned on the bladeof each wafer handler 17, 19 to avoid breaking or damaging the wafer (bythe wafer falling or striking a chamber component), to ensure properplacement of the wafer on a wafer pedestal so as to prevent depositionof material on the wafer pedestal during processing and to ensurecomplete coverage during deposition of a material layer on the wafer,etc. Accordingly, to ensure accurate wafer positioning (so as to avoidwafer damage/breakage or deposition on a wafer pedestal, so as to ensurecomplete material layer coverage on a wafer, etc.), numerous waferdetection devices (e.g., sensor systems) exist in fabrication tools todetermine a wafer's position. Such sensor systems are typically locatedin the transfer chambers 13, 15, although sensor systems may be locatedin other chambers as well. A fabrication tool may employ multiple sensorsystems.

Two main types of sensor systems are conventionally used withinfabrication tools. Both systems employ sensors to detect a wafer'sposition as the wafer enters and/or leaves a chamber. In the firstsystem, a sensor is mounted to the outside of a processing chamber andmonitors wafer position via a quartz window formed in the processingchamber. That is, a wafer is observed through the quartz window as thewafer enters and exits the processing chamber. In the second system, asensor is mounted within a transfer chamber and monitors a wafer'sposition as the wafer enters and exits the transfer chamber. The twoconventional sensor systems may be used individually or jointly in thefabrication tool 11.

Both types of sensor systems have disadvantages. With regard to thefirst sensor system, material may deposit on the quartz window duringprocessing and affect sensor resolution/accuracy. With regard to thesecond system, sensor mounting locations typically must be machinedwithin the transfer chamber (e.g., a potentially difficult and timeconsuming process).

FIG. 1B is a partially exploded perspective view of the transfer chamber15 of FIG. 1A that is useful in explaining another conventional sensorsystem. The transfer chamber 13 of FIG. 1A may be similarly configured.

As stated, in one conventional sensor system, a sensor may be mountedwithin a transfer chamber and monitor a wafer's position as the waferenters and exits the transfer chamber. For example, in FIG. 1B, aplurality of light transmitters 39 a-b (shown in phantom) are mounted toa lid 41 of the transfer chamber 15 (e.g., to one or more quartz windowsor viewports not shown) and generate light beams 44 a-b (shown inphantom) that are directed toward a bottom 43 of the transfer chamber15. A plurality of receivers 45 a-b (e.g., photodetectors) are mountedto the bottom 43 of the transfer chamber 15 (e.g., the bottom 43 ismachined to accept the receivers 45 a-b), and are positioned to receivethe light beams 44 a-b generated by the transmitters 39 a-b.

By monitoring when the light beams 44 a-b are broken by a wafer Wpositioned on a blade B (shown in phantom) of the wafer handler 19(e.g., as the wafer W is positioned for entry through a slit 47 of thetransfer chamber 15 and/or as the wafer W travels through the slit 47 ofthe transfer chamber 15), the position of the wafer W on the blade B maybe determined by conventional techniques.

A reflection based system wherein light beams 44 a-b are reflected offof the wafer W toward the receivers 45 a-b also may be employed todetermine wafer position (e.g., if both the transmitters 39 a-b and thereceivers 45 a-b are mounted to either the lid 41 or the bottom 43). Ineither case, machining of one or more of the lid 41 and the bottom 43may be required.

In one conventional system termed an on-the-fly (OTF) center finder, thetransmitters 39 a-b and the receivers 45 a-b are employed to sense thewafer W as the wafer handler 19 rotates, and to determine wafer centerinformation based thereon. Typically three light transmitters and threereceivers are employed. The three light transmitters conventionally aremounted to the bottom 43 of the transfer chamber 15, outside thetransfer chamber 15. Holes are machined in the bottom 43 to allow thelight beams from the transmitters to travel into the transfer chamber15. The three receivers typically are mounted to the lid 41, outside thetransfer chamber 15. Holes are machined in the lid 41 to allow the lightbeams from the transmitters to travel to the receivers.

In operation, the OTF center finder monitors (via the receivers mountedto the lid 41 of the transfer chamber 15) when light beams emitted bythe transmitters mounted to the bottom 43 of the transfer chamber 15 areblocked by the wafer W (e.g., as during such time periods, no lightbeams are detected by the receivers mounted to the lid 41). Acorresponding “blocked” light beam signal is sent to a controller (notshown), and the controller determines a step count of a motor (notshown) that rotates the wafer handler 19. The controller then employs analgorithm to determine the center of the wafer W in relation to thecenter of the wafer handler 19. The wafer W thereby may be placed in anexact location as it travels through the slit 47.

As well as requiring machining of holes in the transfer chamber 15, theOTF center finder suffers from other drawbacks. For example, the wafer Wmay move on the blade B during rotation (after passing the light beams44 a-b). Wafer position determinations thereby may be inaccurate.

Accordingly, an improved method and apparatus is needed for detectingwafer position during wafer transfer.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the invention, a valve/sensorassembly is provided that includes a door assembly. The door assemblyhas (1) a first position adapted to seal an opening of a chamber; (2) asecond position adapted to allow at least a blade of a substrate handlerto extend through the opening of the chamber; and (3) a mountingmechanism adapted to couple the door assembly to the chamber. Thevalve/sensor assembly also includes a sensor system having a transmitterand a receiver adapted to detect a presence of a substrate and tocommunicate through at least a portion of the door assembly.

In a second aspect of the invention, a valve/sensor assembly is providedthat includes a door assembly having (1) a first position adapted toseal an opening of a chamber; (2) a second position adapted to allow atleast a blade of a substrate handler to extend through the opening ofthe chamber; and (3) a mounting mechanism adapted to couple the doorassembly to the chamber, the mounting mechanism having a viewport. Thevalve/sensor assembly also includes a sensor system having a transmitterand a receiver adapted to detect a presence of a substrate and tocommunicate through the viewport of the mounting mechanism.

Systems, methods and computer program products are provided inaccordance with these and other aspects of the invention. Each computerprogram product may comprise a medium readable by a computer (e.g., acarrier wave signal, a floppy disk, a compact disk, a hard drive, etc.).

Other features and aspects of the present invention will become morefully apparent from the following detailed description, the appendedclaims and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic top plan view, in pertinent part, of aconventional automated semiconductor device fabrication tool;

FIG. 1B is a partially exploded perspective view of the transfer chamberof FIG. 1A that is useful in explaining conventional sensor systems;

FIG. 2 is a partial sectional view of the fabrication tool of FIG. 1Ataken along the line 2—2 of FIG. 1A, which shows an angled doorassembly;

FIGS. 3A-B are side views of the angled door assembly of FIG. 2 in anopened and closed position, respectively;

FIG. 4 is a perspective view of a first inventive valve/sensor assemblythat employs an angled door assembly that is similar to the angled doorassembly of FIGS. 2-3B;

FIG. 5 is a schematic side elevational view of a conventional verticaldoor assembly;

FIG. 6 is a side perspective view of a second inventive valve/sensorassembly;

FIG. 7 is a top view of the second inventive valve/sensor assembly ofFIG. 6;

FIG. 8 is a bottom perspective view of the second inventive valve/sensorassembly of FIG. 6;

FIG. 9 is a perspective view of the second inventive valve/sensorassembly of FIG. 6 shown coupled to the transfer chamber of FIG. 1A;

FIG. 10 is an exploded isometric view of an alternative, conventionalvertical door assembly that may be used in place of the vertical doorassembly of FIG. 5 within the inventive valve/sensor assembly of FIGS.6-9;

FIG. 11 is a schematic view of a conventional arm employable by thewafer handler of FIGS. 1A and 1B;

FIG. 12 is a side view of an exemplary through-beam sensor system thatmay determine a wafer's position on the blade of FIG. 11 of the waferhandler of FIG. 1A;

FIG. 13 is a flowchart of an exemplary process for determining a wafer'sposition on a wafer handler using the through-beam sensor system of FIG.12; and

FIG. 14 is a partial side view of an exemplary reflection-based sensorsystem that may determine a wafer's position on the blade of FIG. 11 ofthe wafer handler of FIG. 1A.

DETAILED DESCRIPTION

In accordance with the present invention, a novel sensor system isprovided wherein sensors (e.g., transmitters and/or receivers) employedduring conventional wafer position and/or center determinations areattached to and/or may communicate through a door assembly (e.g., a slitvalve bracket) employed to seal an opening of a transfer chamber (e.g.,the slit 47 of FIG. 1B). In this manner, additional holes or sensormounting locations need not be machined within the transfer chamber(e.g., within the bottom 43 of the transfer chamber 15 of FIG. 1B).Sensors may be positioned such that a light beam is broken by a waferjust before the wafer exits the transfer chamber (e.g., as the waferenters the slit 47 and travels to a processing chamber such as one ofthe processing chambers 29-35 of FIG. 1A). In this manner, as comparedto an OTF center finder, a wafer is significantly less likely to move(e.g., relative to a wafer handler blade that supports the wafer) afterthe wafer passes the sensors or exits the transfer chamber.Additionally, controller software employed during wafer positioningcalculations is simplified because sensors may be positioned so thatonly wafers exiting the transfer chamber may break the light beams ofthe sensors (e.g., other wafers being transported between processingchambers, or portions of a wafer handler cannot inadvertently break thelight beam of a sensor). Only one sensor bank per transfer chamberopening is required.

As stated, the inventive sensor system employs sensors attached to adoor assembly that seals an opening of a transfer chamber. In general,any type of door assembly may be so configured (e.g., gate valveassemblies, slit valve assemblies, etc.). Several exemplary doorassemblies configured in accordance with the present invention aredescribed below. It will be understood that other door assemblies may besimilarly configured.

Conventional Angled Door Assembly

FIG. 2 is a partial sectional view of the fabrication tool 11 of FIG. 1Ataken along the line 2—2 of FIG. 1A, which shows an angled door assembly37 a. The angled door assembly 37 a includes a sealing surface 38 a thattypically moves up and down at a 45 degree angle (shown by angle X inFIG. 2) relative to a bottom wall 139 of the transfer chamber 15 so asto selectively engage and seal a sealable opening 143 a (e.g., a slit)of the transfer chamber 15 as shown in FIG. 2.

FIGS. 3A-B are side views of the angled door assembly 37 a of FIG. 2 inan opened and closed position, respectively, and illustrate the angleddoor assembly 37 a in more detail than that shown in FIG. 2. The sealingsurface 38 a of the angled door assembly 37 a moves between the openedposition (FIG. 3A) wherein the angled door assembly 37 a does not sealthe opening 143 a and the closed position (FIG. 3B) wherein the angleddoor assembly 37 a seals the opening 143 a.

As shown in FIGS. 3A-B, the opening 143 a is surrounded by a valve seat165, whereby the sealing surface 38 a of the angled door assembly 37 aselectively engages the valve seat 165 to close the opening 143 a. Thesealing surface 38 a of the angled door assembly 37 a may have a groove(not shown) formed therein to contain an O-ring 172. The sealing surface38 a is positioned to contact the valve seat 165 when the angled doorassembly 37 a is in a closed position (FIG. 3B).

The angled door assembly 37 a also may comprise an elongated shaftportion 173 (of an actuator assembly 175) that allows the angled doorassembly 37 a to move between the opened position (FIG. 3A) and theclosed position (FIG. 3B). The actuator assembly 175 may comprise acylinder 177 that has a piston 179 that drives the shaft port 173 (andthe sealing surface 38 a coupled thereto) between the opened and closedpositions. The angled door assembly 37 a may be configured, for example,as described in U.S. Pat. No. 5,363,872, issued Nov. 15, 1994, theentire disclosure of which is incorporated herein by this reference.

In operation, the wafer handler 19 (FIG. 1A or FIG. 1B) transfers thewafer W toward the sealable opening 143 a (e.g., slit 47 in FIG. 1B). Asthe wafer handler 19 approaches the sealable opening 143 a, the sealingsurface 38 a of the angled door assembly 37 a, upon actuation, moves tothe opened position (FIG. 3A) so as to allow the blade of the waferhandler 19 to extend through the opening 143 a. The wafer W then may betransferred to another chamber via the blade of the wafer handler 19.

First Inventive Valve/Sensor Assembly

FIG. 4 is a perspective view of a first inventive valve/sensor assembly445 that employs an angled door assembly 437 that is similar to theangled door assembly 37 a of FIGS. 2-3B. The inventive valve/sensorassembly 445 may detect the position of a wafer within a chamber such asone of the transfer chambers 13, 15 of FIG. 1A.

With reference to FIG. 4, the inventive valve/sensor assembly 445includes a mounting mechanism 447 for mounting the angled door assembly437 to a bottom of a transfer chamber (e.g., to the bottom 43 of thetransfer chamber 15 of FIG. 1B), a sensor system 448 and a controller449 coupled to the sensor system 448. The angled door assembly 437 maybe positioned so as to seal one of the various slits of the transferchamber 15, such as slit 47 in FIG. 1B as described previously withreference to the door assembly 37 a of FIGS. 2-3B.

The sensor system 448 may detect the position of a wafer and may outputa signal indicative of the position of the wafer by using one or moreconventional techniques. The controller 449 may receive the signaloutput by the sensor system 448. In the exemplary embodiment of FIG. 4,the sensor system 448 includes a light transmitter 451, such as one ormore light emitting diodes (LEDs), and a receiver 453, such as one ormore photodetectors.

In one embodiment, the mounting mechanism 447 is configured to couple tothe bottom wall 43 (shown in phantom in FIG. 4) of the transfer chamber15, via bolts or some other fastener (not shown). The mounting mechanism447 may comprise a bracket that includes a horizontal mounting platform457 adapted to couple to the bottom wall 43 of the transfer chamber 15,and two vertical sidewalls 459 a, 459 b coupled to the horizontalmounting platform 457. The mounting platform 457 and the sidewalls 459a, 459 b may be machined from a single piece of material (if desired).Any other configuration may be similarly employed.

The horizontal mounting platform 457 comprises an opening (not shown) inwhich the angled door assembly 437 is mounted, and a viewport 463. Inone or more embodiments of the invention, the viewport 463 allows thelight transmitter 451 and the receiver 453 to communicate as describedbelow. The viewport 463 may comprise, for example, a quartz window thatallows a light beam to travel therethrough, and the light transmitter451 and/or the receiver 453 to be isolated from the environment of thetransfer chamber 15.

In the embodiment of FIG. 4, the light transmitter 451 is coupled to thelid 41 of the transfer chamber 15 (e.g., is mounted to the lid 41outside the transfer chamber 15), and generates a plurality of lightbeams 465 a-b which travel through the lid 41 (e.g., through a pluralityof holes 467 a-b in the lid 41, or one or more quartz windows orviewports (not shown) of the lid 41) into the transfer chamber 15 towardthe viewport 463. When not obstructed by the wafer W, the light beamstravel through the viewport 463 and are detected by the receiver 453.

The receiver 453, for example, may be coupled to the mounting mechanism447 or otherwise disposed below the viewport 463. Alternatively, thetransmitter 451 may be disposed below the viewport 463, and the receiver453 may be coupled to the lid 41. If a reflection-based system isemployed, both the transmitter 451 and the receiver 453 may be coupledto the mounting mechanism 447 (or otherwise disposed below the viewport463). In either case, because the transmitter 451 and the receiver 453communicate through the inventive valve/sensor assembly 445, additionalmounting locations and/or holes need not be machined within the bottom43 of the transfer chamber 15 to allow the transmitter 451 and thereceiver 453 to communicate. Note that more or fewer than twotransmitters and receivers may be employed.

In operation, as the wafer W leaves the transfer chamber 15 (or as thewafer W re-enters the transfer chamber 15) from any of the variouschambers coupled thereto, the wafer W breaks one or both of the lightbeams 467 a-b. In response thereto, a signal (e.g., from the receiver453) is communicated to the controller 449. The controller 449 then maycompute the position of the wafer W on the wafer handler 19 using anyconventional technique. For example, a position value may be computedfor the wafer W and compared to a position value previously stored for awafer properly positioned on the wafer handler 19. Based thereon, awafer offset value may be calculated. If the wafer W is misaligned(e.g., if the position of the wafer W is off-center relative to a bladeof the wafer handler 19), the wafer handler 19 may then center the waferW relative to an opening (e.g., slit 47 in FIG. 1B) through which thewafer W is to travel or relative to a wafer support on which the wafer Wis to be placed (e.g., using any conventional wafer-positioningtechnique).

As previously stated, any conventional door assembly may be configuredwith a sensor system in accordance with the present invention.Accordingly, exemplary, additional embodiments of the present inventionare described further below.

First Conventional Vertical Door Assembly

FIG. 5 is a schematic side elevational view of a conventional verticaldoor assembly 37 b. The vertical door assembly 37 b includes a sealingsurface 38 b that moves up and down parallel to a surface 544 (e.g., asurface of the transfer chamber 15 of FIG. 1A or of a processingchamber) having a sealable opening 543 b (e.g., slit 47 in FIG. 1B),rather than moving at a 45 degree angle as with the angled door assembly37 a of FIG. 2.

The vertical door assembly 37 b may comprise a paddle-shaped structure545, having the sealing surface 38 b coupled to an elongated shaftportion 547 that extends downward from the sealing surface 38 b. Thevertical door assembly 37 b also may comprise a first air cylinder 549a, coupled to a lower portion 551 of the paddle-shaped structure 545,that allows movement of the sealing surface 38 b between a loweredposition (not shown) wherein the vertical door assembly 37 b does notocclude the opening 543 b and an elevated position (FIG. 5) wherein thesealing surface 38 b occludes the opening 543 b. When the sealingsurface 38 b is in the elevated position (FIG. 5), upon actuation, asecond air cylinder 549 b pushes against the lower portion 551 so as topivot the sealing surface 38 b toward and into contact with the sealableopening 543 b. The sealing surface 38 b thereby seals the sealableopening 543 b.

Second Inventive Valve/Sensor Assembly

FIGS. 6-9 show various views of a second inventive valve/sensor assembly645 that employs the vertical door assembly 37 b of FIG. 5.Specifically, FIG. 6 is a side perspective view of the second inventivevalve/sensor assembly 645; FIG. 7 is a top view of the second inventivevalve/sensor assembly 645; FIG. 8 is a bottom perspective view of thesecond inventive valve/sensor assembly 645; and FIG. 9 is a perspectiveview of the second inventive valve/sensor assembly 645 shown coupled tothe transfer chamber 15.

The inventive valve/sensor assembly 645 may comprise a mountingmechanism 647, a sensor system 688 (represented by a transmitter 688 aand a receiver 688 b shown in phantom), and a controller 649 coupled tothe sensor system 688. As with the sensor system 448 of the firstinventive valve/sensor assembly 445, the sensor system 688 may detectthe position of a wafer by using one or more of the previously describedtechniques, or one or more of the techniques described below with FIGS.12-14. The controller 649 may receive a signal output by the sensorsystem 688 (e.g., a signal from the receiver 688 b of the sensor system688 that indicates when a light beam transmitted from the transmitter688 a to the receiver 688 b has been blocked). The inventivevalve/sensor assembly 645 may include multiple sensor systems 688, thetransmitter 688 a may include multiple light sources and/or the receiver688 b may include multiple light detectors. The locations of thetransmitter 688 a and the receiver 688 b are merely exemplary.

In one embodiment, the mounting mechanism 647 may comprise a housing(e.g., a structure that may be inserted between a transfer chamber andanother chamber, and that contains a conventional door assembly adaptedto engage and seal a sealable opening such as the door assembly 37 b ofFIG. 5) that is coupled to a sidewall 682 (FIG. 9) of the transferchamber 15, via bolts or some other fastener (not shown). The housingmay comprise an adapter block 683 having an opening that may accommodatedifferent wafer sizes and that may accommodate different sealing platesizes.

In the embodiments of FIGS. 6-9, the adapter block 683 comprises arectangular-shaped structure that has six sides. A bottom wall 685 (FIG.8) has a region (not shown) that allows the vertical door assembly 37 bof FIG. 5 to move up and down so as to selectively seal an opening ofthe transfer chamber 15, such as the slit 47 of FIG. 1B. A top wall 689(FIG. 7) and the bottom wall 685 (FIG. 8) may have a top slot 693 (FIG.7) and a bottom slot 695 (FIG. 8), respectively, such that thetransmitter 688 a and/or the receiver 688 b may be inserted therein. Forexample, the light transmitter 688 a may be inserted in the top slot 693(FIG. 7), and the receiver 688 b may be inserted in the bottom slot 695(FIG. 8). For embodiments that employ reflection-based sensor systems(as described below with reference to FIG. 14), the top slot 693 or thebottom slot 695 may contain both the transmitter 688 a and the receiver688 b. Both slots 693, 695 may contain a quartz window, such that eachrespective sensor may be isolated from processing tool environments.

The top wall 689 may comprise a viewport 663 b (FIG. 7) and/or maycomprise a removable lid 697 (FIG. 7), coupled to the remainder of theinventive valve/sensor assembly 645, via a latching mechanism 698 (FIG.7). The viewport 663 b (e.g., a quartz window) may provide unobstructedview of a wafer as the wafer passes through the inventive valve/sensorassembly 645. The removable lid 697 provides access into the adapterblock 683 so as to allow repair of the vertical door assembly 37 b or soas to allow cleaning of the adapter block 683 and/or the sensor system688. A front wall 699 (FIG. 6) and a back wall 700 (FIG. 8) each have anaperture 703 (FIG. 6), 705 (FIG. 8) aligned so as to allow the waferhandler 19 and a wafer positioned thereon to pass through the adapterblock 683 as the wafer handler 19 transports the wafer between thetransfer chamber 15 and another chamber coupled thereto.

In operation, the wafer handler 19 transfers a wafer toward the sealableopening 543 b (FIG. 5). As the wafer handler 19 approaches the sealableopening 543 b, the vertical door assembly 37 b, upon actuation, moves toa lowered position so as to allow a blade of the wafer handler 19 toextend through the opening 543 b and through the adapter block 683. Awafer thereby may be transferred through the inventive valve/sensorassembly 645 and into another chamber.

Unlike the inventive valve/sensor assembly 445 of FIG. 4, which detectsthe position of a wafer while it is still within the transfer chamber15, the inventive valve/sensor assembly 645 of FIGS. 6-9 detects theposition of a wafer as the wafer passes through the adapter block 683(e.g., using one or more of the previously described techniques, or oneor more of the techniques described below with reference to FIGS.12-14).

Because the exact locations of the light transmitter 688 a and thereceiver 688 b are known relative to each other, the number of variablesof the sensor system 688 is reduced, which may simplify the calibrationrequirements. Further, the modularity of the adapter block 683 allowsthe inventive valve/sensor assembly 645 to be easily replaced orrepaired.

Although the inventive valve/sensor assembly 645 has been described withreference to the vertical door assembly 37 b of FIG. 5, it will beunderstood that other door assemblies may be used in place of thevertical door assembly 37 b, such as the vertical door assembly of FIG.10 (described below).

Second Conventional Vertical Door Assembly

FIG. 10 is an exploded isometric view of an alternative, conventionalvertical door assembly 37 c that may be used in place of the verticaldoor assembly 37 b of FIG. 5 within the inventive valve/sensor assembly645 of FIGS. 6-9. As stated, any other conventional vertical doorassembly may be similarly employed.

With reference to FIG. 10, the vertical door assembly 37 c employs atleast one inflatable member 1111 adapted to selectively move afrontplate 1113 of the vertical door assembly 37 c toward a sealableopening (not shown), such as the sealable opening 543 b of FIG. 5. Thevertical door assembly 37 c also may include a backplate 1115 coupled tothe frontplate 1113. The inflatable member 1111 is disposed between thefrontplate 1113 and the backplate 1115 and is adapted to move thefrontplate 1113 into sealing engagement with an opening of a chamber(e.g., the slit 47 of FIG. 1B) when inflated. The vertical door assembly37 c may be configured as described in U.S. patent application Ser. No.09/238,251, filed Jan. 27, 1999 (AMAT No. 2826/ATD/MBE) the entiredisclosure of which is incorporated herein by this reference. Theinventive valve/sensor assembly 645 operates similarly whether the doorassembly 37 b (FIG. 5) or the door assembly 37 c (FIG. 10) is employed.

Conventional Arm of Wafer Handler

FIG. 11 is a schematic view of a conventional arm 1117 employable by thewafer handler 19 of FIGS. 1A and 1B. The arm 1117 may be employed duringwafer positioning and/or centering in accordance with the presentinvention. Any other conventional wafer handler arm may be similarlyemployed.

With reference to FIG. 11, the arm 1117 may comprise a wrist 1119, ablade 1121 mounted to the wrist 1119, a pair of grippers 1123 positionedat the proximal end of the blade 1121, and a pair of projections or“shoes” 1125 positioned at the distal end of the blade 1121. The shoes1125 and the grippers 1123 are positioned to form a pocket 1127 suchthat a wafer W (shown in phantom) may be inserted into the pocket 1127.The blade 1121 comprises a center hole 1129, which may be used todetermine the presence of the wafer W on the blade 1121 as describedbelow, and a slot 1131 positioned adjacent the grippers 1123, which maybe used to determine the position of the wafer on the blade 1121 also asdescribed below.

Upon actuation of a stepper motor (not shown), the grippers 1123, whichare described in detail in U.S. Pat. No. 5,980,194, issued Nov. 9, 1999,the entire disclosure of which is incorporated herein by this reference,may retract away from the projections 1125 to enlarge the pocket 1127 asthe wafer W is inserted onto the blade 1121. The grippers 1123 then mayextend toward the projections 1125 to close the pocket 1127 after thewafer W is placed onto the blade 1121, thereby clamping the wafer W inthe pocket 1127.

During operation of the wafer handler 19 (when the arm 1117 is employed)with the inventive valve/sensor assembly 445 of FIG. 4 (or the inventivevalve/sensor assembly 645 of FIG. 6), the controller 449 (or thecontroller 649) may count the number of steps (e.g., of a stepper motor(not shown) that drives the wafer handler 19) that the wafer handler 19has moved between one reference point (e.g., a point where the edge ofthe wafer W blocks a light beam from transmitter 451 or 688 a fromreaching receiver 453 or 688 b) and another reference point (e.g., apoint where the slot 1131 allows the light beam to pass therethrough andto the receiver 453 or 688 b). The controller 449 (or the controller649) then may derive an offset for proper positioning of the wafer W.

Positioning techniques may function by using the following generalprocess. First, the sensor system 448, 688 is calibrated by collectingdata from a wafer that is properly positioned on the blade 1121. Then,to determine the position of a wafer being processed in the tool 11(FIG. 1A), positional points are collected when an edge of the slot 1131crosses a light beam (from transmitter 451 or 688 a) and when an edge ofthe wafer crosses the light beam. The positional points are compared tothe calibration data to calculate a wafer offset value. From the waferoffset value, the wafer handler 19 may center the wafer on a substratesupport (not shown) of another chamber (e.g., one of the processingchambers 29-35 of FIG. 1A) by adjusting the position of the blade 1121relative to the substrate support (such that the wafer is centered abovethe wafer support).

Exemplary Through-Beam Sensor System

FIG. 12 is a side view of an exemplary through-beam sensor system 1201that may determine a wafer's position on the blade 1121 (FIG. 11) of thewafer handler 19 (FIG. 1A). A similar through-beam sensor system may beemployed with the inventive valve/sensor assemblies 445, 645. Withreference to FIG. 12, the through-beam sensor system 1201 comprises atransmitter 1203 positioned so as to transmit a light beam 1205 to areceiver 1207 “through” a path traveled by the wafer handler 19 as thewafer handler 19 transports a wafer W. The transmitter 1203 may bepositioned, for example, on the lid 41 of the transfer chamber 15, andthe receiver 1207 may be coupled to the mounting plate 457 of theinventive valve/sensor assembly 445. Other locations may be similarlyemployed. As described further below, when the wafer W is positionedbetween the transmitter 1203 and the receiver 1207, the wafer W blocksthe light beam 1205 emitted by the transmitter 1203, and the receiver1207 does not detect the light beam 1205. When the wafer W is notpositioned between the transmitter 1203 and the receiver 1207, thereceiver 1207 detects the light beam 1205.

Exemplary Process for Through-Beam Sensor System

FIG. 13 is a flowchart of an exemplary process 1300 for determining awafer's position on the wafer handler 19 using the through-beam sensorsystem 1201 of FIG. 12. Other processes may be similarly performed.

Referring to FIG. 13, in step 1301, the sensor system 1201 is calibratedby collecting data from a wafer that is properly centered on the blade1121 of the wafer handler 19 as the wafer travels between thetransmitter 1203 and the receiver 1207. The data may include, forexample, (1) a measured distance between a trailing edge of the properlycentered wafer and a trailing edge of the slot 1131; (2) the size of thewafer (e.g., 5, 6, or 8 inch); (3) a measured distance between two ormore reference points, as the wafer handler 19 transports the properlycentered wafer; (4) a measured distance between the leading and thetrailing edges of the slot 1131; (5) the location of the transmitter1203 and the receiver 1207; and (6) the speed at which the blade 1121 ofthe wafer handler 19 travels. The data is stored and is used todetermine a wafer offset value of a wafer W (e.g., a subsequent, notnecessarily properly centered wafer) that is transported by the waferhandler 19 as described below. The data may be stored, for example, in acontroller 1249 (FIG. 12), the controller 449 (FIG. 4), the controller649 (FIG. 6) or the like.

In step 1303, the wafer handler 19 transports the wafer W from thetransfer chamber 15 to one of the various chambers coupled to thetransfer chamber 15 (e.g., one of the processing chambers 29-35). As thewafer handler 19 transports the wafer W from the transfer chamber 15 toanother chamber, the leading edge of the wafer W (the distal edge of thewafer W on the blade 1121) blocks the light beam 1205 from thetransmitter 1203 so that the receiver 1207 does not detect the lightbeam 1205. After the wafer W passes the light beam 1205, the slot 1131allows the light beam 1205 to pass through the wafer handler 19 so as tocontact the receiver 1207.

In step 1305, the change in the amount of light detected by the receiver1207 between when the wafer W interrupts the light beam 1205 and whenthe slot 1131 allows the light beam 1205 to pass through the waferhandler 19 is determined. Note that an output of the receiver 1207 mayhave a first signal value when the light beam 1205 contacts the receiver1207 (e.g., a non-interrupted state such as when the light beam 1205passes through the slot 1131), and may have a second signal value whenthe light beam 1205 does not contact the receiver 1207 (e.g., aninterrupted state such as when the light beam 1205 strikes the wafer W).

The output signal of the receiver 1207 thus changes from the firstsignal value to the second signal value when the light beam 1205 (whichstrikes the receiver 1207 before the wafer handler 19 crosses the pathof the light beam) becomes blocked by the leading edge of the wafer W.After the trailing edge of the wafer W passes the light beam 1205, theoutput signal of the receiver 1207 changes from the second signal valueto the first signal value when the light beam 1205 passes through theslot 1131. After the trailing edge of the slot 1131 passes the lightbeam 1205, the output signal of the receiver 1207 changes from the firstsignal value back to the second signal value.

In step 1307, the controller 1249 counts the number of steps that theblade 1121 of the wafer handler 19 has moved between when the outputsignal of the receiver 1207 changes from the second signal value(interrupted state) to the first signal value (non-interrupted state)and back to the second signal value (interrupted state) (e.g., the timeperiod during which the receiver 1207 outputs the first signal value).The controller 1249 converts the step count into a position value instep 1309 (e.g., by means of lookup table that stores the calibratedvalues previously described). Then, in step 1311, the position value iscompared to the calibrated data to calculate a wafer offset value.Specifically, an exact match between the position value for the wafer Wand the position value previously stored for the properly centered wafer(step 1301) represents a centered wafer. If the position value for thewafer W differs from the position value previously stored for theproperly centered wafer, then the wafer W is not properly centered.

In step 1312, the wafer offset value is compared to a predeterminedvalue. If the wafer offset value is greater than the predeterminedvalue, in step 1313, the controller 1249 may stop the wafer handler 19so that an operator may manually center the wafer W on the blade 1121(and the process 1300 may end); otherwise, in step 1315, if the waferoffset value does not exceed the predetermined value, then wafertransfer continues as described below.

Following step 1315, in step 1317, the controller 1249 calculatescorrection values for the wafer handler 19 from the wafer offset value.Based on the correction values, the controller 1249 alters the linearand/or rotational translations of the wafer handler 19 so as to adjustfor wafer misalignment and to center the wafer W (step 1319). The waferW also may be centered using the technique described in U.S. Pat. No.5,563,798, issued October, 1996, the entire disclosure of which isincorporated herein by this reference. Assuming the wafer handler 19transports the wafer W from the transfer chamber 15 to the processingchamber 29, the wafer W may be placed on (e.g., centered on) a substratesupport (not shown) of the processing chamber 29 and processed.

In step 1321, the wafer handler 19 transports the wafer W from a chambercoupled to the transfer chamber 15 (e.g., one of the processing chambers29-35 of FIG. 1A) to the transfer chamber 15. As the wafer handler 19transports the wafer W to the transfer chamber 15, the slot 1131 allowsthe light beam 1205 to pass through the wafer handler 19 so as tocontact the receiver 1207. After the slot 1131 passes the light beam1205, the leading edge of the wafer W blocks the light beam 1205.

In step 1323, the change in the output signal of the receiver 1207between when the slot 1131 allows the light beam 1205 to pass throughthe wafer handler 19 and when the leading edge of the wafer W interruptsthe light beam 1205 is determined. When the slot 1131 allows the lightbeam 1205 to pass, the output signal of the receiver 1207 is the firstsignal value. When the leading edge of the wafer W interrupts the lightbeam 1205, the output signal of the receiver 1207 is the second signalvalue.

The output signal of the receiver 1207 changes from the first signalvalue to the second signal value when the light beam 1205 travelingthrough the slot 1131 becomes blocked by the leading edge of the waferW. In step 1325, the controller 1249 counts the number of steps that thewafer handler 19 has moved while the light beam 1205 passes through theslot 1131 (e.g., the time period during which the receiver 1207 outputsthe first signal value). The controller 1249 converts the step countinto a position value in step 1327. Then, in step 1329, the positionvalue is compared to the calibrated data to calculate the wafer offsetvalue. Thereafter, in step 1331, the wafer W is centered as describedabove with reference to steps 1312-1319. The process 1300 then ends.

As stated previously, the inventive valve/sensor assembly 445 of FIG. 4,the inventive valve/sensor assembly 645 of FIG. 6 or any othervalve/sensor assembly configured in accordance with the presentinvention may employ the process 1300 or a variation thereof. Thecontroller 449, 649 and/or 1249 may comprise computer program code forperforming one or more of the steps of the process 1300 and may includeone or more computer program products.

Exemplary Reflection-Based Sensor System

FIG. 14 is a partial side view of an exemplary reflection-based sensorsystem 1401 that may determine a wafer's position on the blade 1121(FIG. 11) of the wafer handler 19 (FIG. 1A). A similar reflection-basedsensor system may be employed with the inventive valve/sensor assemblies445, 645 or any other valve/sensor assembly configured in accordancewith the present invention.

With reference to FIG. 14, the refection-based sensor system 1401comprises a transmitter 1403 and a receiver 1405, which may or may notbe contained within a single housing 1407. The transmitter 1403 and thereceiver 1405 may be located in, for example, the top slot 693 of theinventive valve/sensor assembly 645 (FIG. 7). The receiver 1405 maydetect a light beam 1409 (transmitted by the transmitter 1403) thatreflects off of the wafer W, to indicate wafer presence (rather thandetect a light beam that passes between a light transmitter and areceiver to indicate wafer absence as with the through-beam sensor 1201of FIG. 12).

Thus, for the reflection-based sensor system 1401, the change in theoutput signal of the receiver 1405 is measured when the slot 1131 allowsthe light beam 1409 to pass therethrough as compared to when the wafer Wreflects the light beam 1409 toward the receiver 1405. When the lightbeam 1409 passes through the slot 1131, the output signal of thereceiver 1405 has a first signal value (interrupted state). When thewafer W reflects the light beam 1409, the output signal of the receiver1405 has a second signal value (non-interrupted state). The change inthe output signal of the receiver 1405 may be used for wafer positioningin a manner similar to that of process 1300 (FIG. 13).

Both the through-beam sensor system 1201 (FIGS. 12-13) and thereflection-based sensor system 1401 (FIG. 14) may determine whether thewafer W is present on the blade 1121. As the wafer handler 19 passesthrough the sensor system 1201, 1401, the light beam 1205, 1409 may passthrough the center hole 1129 (FIG. 11) of the blade 1121 if the wafer Wis not present on the blade 1121. Otherwise, if the wafer W is presenton the blade 1121, the wafer W blocks the light beam 1205, 1409.Detection of the leading or trailing edge of the wafer W similarly mayindicate wafer presence. The light beam 1205, 1409 may be projected atan angle relative to either the lid 41 of the transfer chamber 15 or thetop slot 693 of the inventive valve/sensor assembly 645. The angledlight beam may reduce the possibility that the receiver 1207, 1405 willdetect other sources of light.

The foregoing description discloses only exemplary embodiments of theinvention. Modifications of the above-disclosed apparatus and methodwhich fall within the scope of the invention will be readily apparent tothose of ordinary skill in the art. As previously described, theinventive valve/sensor assembly 445, 645 may be employed with anyconventional door assembly, may include the use of a reflector asdescribed in U.S. Pat. No. 5,980,194, and may center a wafer using anyconventional wafer-positioning technique.

While the inventive valve/sensor assemblies of the present inventionhave been described primarily with reference to the fabrication tool 11and the transfer chamber 15 (FIG. 1A), it will be understood that thetransfer chamber 13 or any other chamber or fabrication tool may besimilarly configured

Accordingly, while the present invention has been disclosed inconnection with exemplary embodiments thereof, it should be understoodthat other embodiments may fall within the spirit and scope of theinvention, as defined by the following claims.

The invention claimed is:
 1. A door assembly having: a first positionadapted to seal an opening of a chamber; a second position adapted toallow at least a blade of a substrate handler to extend through theopening of the chamber; and a mounting mechanism adapted to couple thedoor assembly to the chamber, the mounting mechanism having a viewportadapted to allow at least one transmitter and at least one receiver tocommunicate through the viewport of the mounting mechanism so as todetect a presence of a substrate.
 2. A mounting mechanism adapted tocouple a door assembly to a chamber, the mounting mechanism having aviewport adapted to allow at least one transmitter and at least onereceiver to communicate through the viewport of the mounting mechanismso as to detect a presence of a substrate.
 3. A method comprising:providing a chamber having a valve/sensor assembly comprising: a doorassembly having: a first position adapted to seal an opening of thechamber; a second position adapted to allow at least a blade of asubstrate handler to extend through the opening of the chamber; and amounting mechanism coupled to the chamber; and a sensor system having atransmitter and a receiver adapted to detect a presence of a substrateand to communicate through at least a portion of the door assembly;transporting a substrate through the opening of the chamber with asubstrate handler; and detecting whether the substrate is on thesubstrate handler with the sensor system.
 4. The method of claim 3further comprising determining whether the substrate is centered on ablade of the substrate handler.
 5. The method of claim 4 furthercomprising adjusting placement of the substrate on a substrate pedestalif the substrate is not centered on the blade of the substrate handler.6. A method comprising: providing a chamber having a valve/sensorassembly comprising: a door assembly having: a first position adapted toseal an opening of the chamber; a second position adapted to allow atleast a blade of a substrate handler to extend through the opening ofthe chamber; and a mounting mechanism coupled to the chamber; and asensor system having a transmitter and a receiver adapted to detect apresence of a substrate and to communicate through at least a portion ofthe door assembly; transporting a substrate through the opening of thechamber with a substrate handler; determining whether the substrate iscentered on a blade of the substrate handler; and adjusting placement ofthe substrate on a substrate pedestal if the substrate is not centeredon the blade of the substrate handler.
 7. A method comprising: providinga chamber having a valve/sensor assembly comprising: a door assemblyhaving: a first position adapted to seal an opening of the chamber; asecond position adapted to allow at least a blade of a substrate handlerto extend through the opening of the chamber; and a mounting mechanismcoupled to the chamber, the mounting mechanism having a viewport; and asensor system having a transmitter and a receiver adapted to detect apresence of a substrate and to communicate through the viewport of themounting mechanism; transporting a substrate through the opening of thechamber with a substrate handler; and detecting whether the substrate ison the substrate handler with the sensor system.